Uniformity control across a semiconductor wafer is becoming more important, especially through nanometer technology. It is becoming more difficult to satisfy advanced semiconductor process requirements in terms of uniformity of etch rate, etch profile, CDU, etch selectivity, residue, deposition rate and so on, using current semiconductor process tools, equipment and methods. Current tools, equipment and methods are generally incapable of achieving the requirements for 45 nanometer (nm) and smaller process technology, and/or 300 mm (˜12-inches in diameter) and larger wafers.
For example, dry process reactor systems are used in semiconductor fabrication for performing various semiconductor processes, such as etching, chemical vapor deposition (CVD), or diffusion. Some dry process reactor systems use a parallel-plate plasma reactor, which typically includes fixed, upper and lower plates or electrodes with a fixed, three-dimensional space therebetween. The upper electrode may be driven by an RF generator to generate and control an ion plasma in the fixed, three-dimensional space between the upper and lower electrodes. Other dry process reactor systems use an inductively coupled plasma (ICP) reactor. An ICP reactor typically includes a fixed, upper coil, a fixed lower plate or electrode, and a fixed, three-dimensional space therebetween. The upper coil may also be driven by an RF generator to generate and control an ion plasma in the fixed, three-dimensional space between the upper coil and lower electrode.
A limitation shared by both the upper coil and the upper electrode is that their physical configuration cannot be adjusted to control the density distribution of the ion plasma. This limitation causes non-uniform device characteristics across the wafer, as semiconductor wafers increase in size and minimum device feature size decreases.
Accordingly, improved upper coils and electrodes are needed which allow the density distribution of the ion plasma to be controlled.